AMD Motherboard with, on board video car...

When the Computer is off install the AGP card and put it together next start the computer when it starts up hit Del key before it boots up go into bios go to devices and disable onboard video, then hit F10 say yes to save changes and reboot it will then detect the card and will ask for drivers for the card. Be sure you read the directions for the video card You may have to install the drivers first, since you did not mention the card brand names and what mother board you have. Asus has many mother boards.